fix(lib/es2015): Fix types of Reflect methods - #41987

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I compared each function to the MDN docs for the reflect API, and that all seems to look right to me - thanks ExE Boss (@ExE-Boss)

ExE Boss (@ExE-Boss) great change, thanks! Looks like lib/lib.es2015.reflect.d.ts needs to be updated for userland code who install via eg. yarn and "typescript": "microsoft/TypeScript#master", in the devDependencies; also tried yarn add -D typescript@next, still getting the old definitions from lib/lib.es2015.reflect.d.ts. Maybe there's some extra build step?

I would like to know what is the return type of Reflect.ownKeys(target) is it of Type '(string | number | symbol)[]' or of Type '(string | symbol)[]' ??? (Sorry to be so confused I am the kind of person who likes to annotate all my functions output types and now I am using /* : (string | number | symbol)[] */ yes with the /* and the */ haha !!!

Benjamin Vincent (@Luxcium) The correct return type of Reflect.ownKeys(target) is (string | symbol)[]:

• https://tc39.es/ecma262/#sec-reflect.ownkeys
• https://tc39.es/ecma262/#sec-invariants-of-the-essential-internal-methods